Thread stretching device for wet spinning more particularly of viscose rayon



Jan. 12, 1960 2,920,346

L. JQRI THREAD STRETCHING DEVICE FOR WET SPINNING MORE PARTICULARLY OF VISCOSE RAYON Filed Feb. 5, 1958 2 Sheets-Sheet 1 Jan. 12. 1960 L. JORI 2,920,346

THREAD STRETCHING DEVICE FOR WET SPINNING MORE PARTICULARLY 0F VISCOSE RAYON 2 Sheets-Sheet 2 Filed Feb. 5. 1958 United States Patent THREAD STRETCHING DEVICE FOR WET-SPIN- ECEHVMORE PARTICULARLY OF VISCOSE Luciano .lori, Milan, Italy Application February 5, 1958, Serial No. 713,395 Claims priority, application Italy August 9, 1957 2 Claims. (Cl. 18-8) In the manufacture of artificial and synthetic threads the practise is widely followed of drawing or stretching the thread as it is formed, in order to modify its structure, hence the properties thereof. Stretching results in orientation of a part of the macromolecules of the thread in the direction of its longitudinal axis, thereby improving its tensile strength.

This process has been long known, actually from the very first attempts made to manufacture threads from high molecular weight substances. It acquired an essential importance in the field of viscose when it was attempted to manufacture thread of high strength capable of industrial application, for instance in tyre manufaeture.

Partly successful endeavours have been made by passing the thread as it issues from the coagulating bath on slub-catchers, .sticks, combs, etc. in order to increase friction, hence traction on the thread being formed. The increment in tensile strength was, however, too moderate.

Pairs of cylinders, rollers or even reels rotating at various peripherical speeds were used, which afforded per se drafts of someimportance, which were merely limited by the drawing attitude and plasticity of the thread. In order to further increase this property it was ascertained that, a part from the choice of the best suited conditions for forming the thread (composition of viscose, composition and temperature of the coagulating bath, etc.), it was necessary to draw and stretch the thread as the latter was immersed in a hot bath. Various liquids were proposed to this effect, but preference was given to water heated to a temperature just slightly below 100 F.

Since stretching was effected by means of members rotating at various peripherical speeds, it was intuitive to adopt for the abovementioned purposes a channel, to the middle of which the stretch-assisting liquid, such as water heated to 95 C. was delivered, this liquid then flowing towards both ends of the channel and discharging into underlaying trays over two weirs in the form, for instance, of V-shaped notches cut in the two endwalls of the channel. The thread undergoing stretching likewise ran across the notches. Such arrangement was actually widely adopted on a number of spinning machines. However, it suffers from various drawbacks:

With the said arrangement the thread travels over the liquid surface. Immersion of the thread is not ensured, nor is the temperature safely maintained on account of the heat dispersion at the liquid surface;

Carbon disulphide evolved from the thread in con-tact with the liquid at high temperature cannot be recovered;

A considerable quantity of salts is formed, more particularly at the thread inlet into the stretching channel, as well as along the thread path, this salt formation being detrimental for the continuity of the elementary filaments forming the thread, giving rise to a hairy appearance.

It has now been found according to this invention that the above drawbacks can be removed by adopting instead of 1a stretching channel a stretching cell. The shape and size of this cell are selected so that notwithstanding a slight section on the liquid running through the cell, over most of the length of the cell a volume remains available which is exclusivelyoccupied by the gases evolving from the thread running through the cell, the said gases issuing through a suitable opening provided in the cell top, The bath should conveniently be supplied to a lower portion of the cell.

Upon selection of the cell length, which depends upon the nature of'the method, time period during which the thread should undergothe actionfof the hot liquid or bath, the cross-sectional area of thecell is preferably of elliptical shape of variable height. The greatest height is at the gas discharge opening.

Nozzles for the inlet and outlet of the thread are provided at both cell ends and serve at the same time as two outlets for the stretch-assisting bath from the cell proper. However, according to an essential aspect of this invention, the two nozzles are not free, each nozzle being arranged within a small chamber. An opening is bored in this chamber'in front of the nozzle for the inlet and outlet of the thread respectively, at the bottom of the small chamber an outlet for the bath being bored. This arrangement creates in the cell and in the two small chambers astearn saturated medium which prevents formation of salt crystals and objectionable consequences thereof,

In present technique stretching is usually carried out by means of two rollers having horizontal axes. It has now been found, more particularly in connection with continuous spinning, which most of the high toughness threadmanufacturers have now decidedly adopted, it is extremelyuseful to operate "with the firs-t roller of the pair having a horizontal axis of. rotation, while-the second; roller which rotates at higher peripheral speed is vertically arranged, more particularly its axis of IO- tation is vertical. much as the parallel arrangement of the threads in an array for successively undergoing the various 'washing, finishing and drying treatments is carried out without any further deflection of the thread, which is extremely advantageous in respect of uniformity of the thread structure and continuity of the filaments composing the thread.

The invention shall be further described by way of example, with reference to the accompanying'drawings, wherein:

Figure 1 is a diagrammatic view of a continuous wet spinning machine;

Figure 2 is a longitudinal vertical sectional view of a stretching cell;

Figure 3 is a detail on a large scale of Figure 2;

Figure 4 is a cross-sectional view on line IVIV of Figure 2, and V Figure 5 shows the roller arrangement with vertical axes.

In Figure 1, 1 denotes the spinning nozzle or spinneret immersed in the coagulating bath, 2 is the thread extruded from the spinneret, 3 the first stretching roller, 4.the stretching cell and 5 the second stretching roller having a vertical axis of rotation.

The thread 2 issuing from the spinneret 1 submerged in the coagulating bath is wound in one or more turns on the first roller 3, runs through the cell 4 and is wound in one or more turns on the roller 5 whence it is conveyed to further treatments.

In Figure 2, which shows the stretching cell on an enlarged scale, 10 denotes an elongated cell casing with 0 end chambers 11, 11', of high moisture content. 12 and 12 denote the two nozzles aligned with the thread inlet and outlet holes 13, 13'; 14 denoting the inlet fitting for This is extremely advantageous, inasthe bath, 15 and 15 the outlets for the bath from the chambers 11, 11' and 16 the gas outlet from the top of the cell 10.

The salts cannot crystallize in the two high moisture chambers 11, 11, so that the nozzles are kept clean and the thread is not damaged by incrustations which would be unavoidable in the absence of the small chambers 11, 11'.

A manner of operating the above described device for manufacturing viscose rayon thread shall now be described by way of example.

Viscose is prepared to a concentration of 7% cellulose with a 6.5% NaOH content, viscosity 30", gamma No. 50.

In order to obtain a thread of 1650 den. this viscose is spun on spinnerets with 850 holes 0.08 mm. in diameter in a coagulating bath containing 7.5% H 80 19% Na SO and 8% ZnSO The bath has been admixed with a quantity of laurylpiridiniurn sulphate in order to lower its surface tension down to 32 dine/cm. determined at a temperature of 67 C., which is the temperature at which the coagulating bath is employed. The thread path in the coagulating bath is 40 cm. long, the peripherical speed of the roller 3 is 27 m./min., the peripherical speed of the roller 5 is 37 m./min.

Water flows through the cell at a temperature of 95 and can absorb up to 1% of the sulphuric acid carried along by the thread from the coagulating bath. The thread is subsequently washed, lubricated and dried.

Figure 5 shows a set of rollers 5 having vertical axes of rotation. It will be seen how the threads 2 from the individual rollers that is from the spinnerets are drawn together to be conveyed towards a washing equipment without any further deflection through the conventional guide stick 20. Thread guides 22 may be arranged on the guide stick 20.

When the thread should be wound on the rollers by a plurality of turns, a finger 21 is employed, the axis of which is inclined to the roller axis or, alternately, is formed with grooves.

The present invention has been described and illustrated according to a preferred embodiment, it being understood that modifications can be made without departing from the scope thereof,

The invention has been moreover described and shown 11 connection with the spinning of viscose rayon, but it will be understood that it can be used in connection with any wet spinning and stretching method imposing similar requirements.

What I claim is:

1. A wet-spinning and stretching apparatus comprising in combination a spinneret immersed in a coagulating bath, a pair of horizontally spaced stretching rollers arranged out of the bath for receiving a thread extruded from the spinneret, and a stretching cell interposed between the stretching rollers, the said cell comprising a horizontally elongated casing of a substantially elliptical cross-section traversed lengthwise by the thread section comprised between the stretching rollers, an inlet for a stretch-assisting liquid at a bottom section of the casing, an outlet for gaseous decomposition products at a top section of the casing, a nozzle at each end of the casing through which the thread can enter and respectively leave the casing and through which the liquid can discharge from the casing, a liquid discharge opening in a bottom section of each collector chamber, and an aperture in a wall section of each chamber facing the respective nozzle, the aperture being aligned with the nozzles whereby the thread can enter and leave the casing passing through the respective chambers.

2. In the apparatus as claimed in claim 1, the stretching roller at the entrance to the cell having a horizontal axis, and the stretching roller at the exit from the cell having vertical axis.

References Cited in the file of this patent UNITED STATES PATENTS 2,228,272 Kinsella Jan. 14, 1941 2,317,448 Dreyfus et al. Apr. 27, 1943 2,450,045 Jackson et al. Sept. 28, 1948 

